1. Field of the Invention
The present invention relates to an endoscope having a treatment tool raising base which is manipulated to change the orientation of a treatment tool which is projected outwardly from the distal end of the insertion portion of the endoscope.
2. Description of the Related Art
Endoscopes provided, in the vicinity of the insertion portion thereof, with a treatment tool raising base that is rotatable are known in the art.
The endoscope disclosed in Japanese Patent Publication No. 3,527,561 is an example of such a type of endoscope. This endoscope is provided with a control portion and an insertion portion which extends from the control portion, and is further provided, at different positions on a surface of the insertion portion in the vicinity of the distal end of the insertion portion, with a raising base accommodation recess and a link member accommodation recess, respectively. The inner end of the link member accommodation recess (the opposite end thereof from the surface of the insertion portion) is communicatively connected with the link member accommodation recess.
This endoscope is further provided with a raising base which is accommodated in the raising base accommodation recess to be rotatable therein, a controller provided on the control portion, and a flexible control wire one end of which is connected to the controller and the other end of which is linked with the raising base. The entire control wire except the distal end thereof (the end of the control wire on the insertion portion side) is inserted into a wire guide conduit provided through the insertion portion and said control portion. The distal end of the control wire is positioned inside the link member accommodation recess.
The endoscope disclosed in Japanese Patent Publication No. 3,527,561 is further provided with a link member for linking the distal end of the control wire with the raising base. This link member is provided with a rotational shaft which extends along the axis of rotation of the raising base and is rotatable on its own axis, and a connecting portion which is connected to the outer end of the rotational shaft and extends orthogonal to the rotational shaft, and the rotational shaft and the connecting portion are formed integral with each other (i.e., non-separable from each other). Accordingly, the overall shape of the link member is in the shape of a substantially letter L.
Additionally, the inner end of the rotational shaft is connected to the raising base to be irrotatable relative to the raising base. The connecting portion of the link member is positioned in the link member accommodation recess, and the distal end of the control wire is connected to the connecting portion of the link member. The position of the connection of the control wire to the connecting portion is offset from the rotational shaft (in a radial direction of the rotational shaft).
Therefore, advancing and withdrawing the control wire along the axis thereof by manipulating the controller causes the link member to rotate forward and reverse about the rotational shaft, thus causing the raising base that is prevented from rotating relative to the rotational shaft (that rotates integrally with the rotational shaft) to rotate forward and reverse relative to the insertion portion.
This endoscope is further provided with a cover which is detachably attached to the insertion portion to close the link member accommodation recess in a watertight fashion so as to cover both the distal end of the control wire and the link member. Accordingly, even if the insertion portion of the endoscope is inserted into a body cavity of a test subject/patient with the cover attached to the insertion portion, there is little possibility of bodily fluids, etc., of the test subject/patient adhering to the control wire (the distal end thereof) or the link member.
Therefore, there is no need to wash either the control wire or the wire guide conduit when the endoscope is cleaned, which makes it possible to perform an endoscope cleaning operation easily (compared with an endoscope which has a structure that partly exposes the control wire and the wire guide conduit, thus requiring the control wire and the wire guide to be washed).
Although the link member accommodation recess is closed in a watertight manner by the cover, the watertight state with the cover cannot be said to be flawless. Accordingly, from the viewpoint of water-tightness, it is desirable that the dimensions of the link member accommodation recess (the area of the opening thereof on the surface of the insertion portion) be made as small as possible.
However, reducing the dimensions of the link member accommodation recess makes it difficult to install and remove the link member to and from the insertion portion (also to and from the raising base). Accordingly, the portion of the control wire which is positioned in the link member accommodation recess (i.e., the aforementioned distal end portion; hereinafter referred also to as the deformable portion) can be deformed (e.g., deformed in a direction sideways away from the insertion portion). However, in the case where the dimensions of the link member accommodation recess are small, the deformable portion of the control wire inevitably becomes small in length, so that the deformable amount of the deformable portion also becomes small; consequently, the degree of freedom in movement of the insertion portion (e.g., in the widthwise direction thereof) becomes small. Therefore, in the case where the length of the rotational shaft of the link member in the axial direction thereof is great, it is difficult to perform an insertion operation to insert the rotational shaft into the link member accommodation recess (and an operation to connect the rotational shaft to the raising base) and a removal operation to remove the rotational shaft from the link member accommodation recess (and an operation to disconnect the rotational shaft from the raising base).